Anatomizing deformation mechanisms in nanocrystalline Pd90Au10
Anatomizing deformation mechanisms in nanocrystalline Pd90Au10
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DOI：
10.1016/j.mechmat.2017.08.010
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发表时间：
2017-11-01
影响因子：
3.9
通讯作者：
Birringer, R.
中科院分区：
文献类型：
--
作者：
Grewer, M.;Braun, C.;Birringer, R.
我们利用基于同步加速器的原位衍射和占主导地位的剪切变形，以确定，解剖，并量化相关的变形机制，在纳米晶Pd 90 Au 10的晶粒尺寸在10 nm或以下的限制情况下。我们可以确定晶格和晶界弹性，剪切洗牌操作的核心区域的晶界，应力驱动的晶界迁移，和位错剪切沿着晶格平面的贡献，但是，有显着不同的和非平凡的应力依赖份额的整体变形。关于晶格弹性，我们发现胡克线性弹性占上风的最大应力值约为1.6 GPa。在/沿着晶界传播应变的剪切洗牌随着载荷的增加而逐渐增加，以在宏观塑性状态下承载约三分之二的总应变。应力驱动的晶界迁移需要克服略低于约1.4GPa的屈服应力的阈值应力，并且对总应变贡献约10%的份额。明显的位错活动开始于约0.9 GPa的应力值，然后增加，并最终传播约15%的总应变的最大份额。在低于0.9 GPa的应力状态下，其特征在于切线模量显著降低，剪切洗牌和晶格和晶界弹性专门操作。在这种制度下的材料响应似乎表示非线性粘性行为，而不是与在传统的面心立方金属中观察到的加工硬化或应变硬化相关。(C)2017爱思唯尔有限公司版权所有
We utilized synchrotron-based in-situ diffraction and dominant shear deformation to identify, dissect, and quantify the relevant deformation mechanisms in nanocrystalline Pd90Au10 in the limiting case of grain sizes at or below 10 nm. We could identify lattice and grain boundary elasticity, shear shuffling operating in the core region of grain boundaries, stress driven grain boundary migration, and dislocation shear along lattice planes to contribute, however, with significantly different and nontrivial stress-dependent shares to overall deformation. Regarding lattice elasticity, we find that Hookean linear elasticity prevailed up to the maximal stress value of approximate to 1.6 GPa. Shear shuffling that propagates strain at/along grain boundaries increases progressively with increasing load to carry about two thirds of the overall strain in the regime of macroplasticity. Stress driven grain boundary migration requires overcoming a threshold stress slightly below the yield stress of approximate to 1.4 GPa and contributes a share of approximate to 10% to overall strain. Appreciable dislocation activity begins at a stress value of approximate to 0.9 GPa to then increase and eventually propagate a maximal share of approximate to 15% to overall strain. In the stress regime below 0.9 GPa, which is characterized by a markedly decreasing tangent modulus, shear shuffling and lattice- and grain boundary elasticity operate exclusively. The material response in this regime seems indicative of nonlinear viscous behavior rather than being correlated with work- or strain hardening as observed in conventional fcc metals. (C) 2017 Elsevier Ltd. All rights reserved.